An electroacoustic actuator usually comprises a housing, in which is arranged at least one loudspeaker, which separates a front volume from a rear volume in the housing. Further, the actuator may have a sound emission pipe, which protrudes outwards from the housing and which is fluidically coupled with the front volume.
Such an electroacoustic actuator may be used in an exhaust system as an active muffler in order to reduce disturbing amplitudes in the noises transported in the exhaust system by means of active noise control. Further, such an actuator may also be used to specifically generate or reinforce certain frequencies in order to operate a so-called sound design. Mixed applications are also conceivable, in which the respective actuator muffles or reduces disturbing frequencies by means of active noise control, while it generates or reinforces desired frequencies at the same time.
For the use of such an actuator, it is basically possible to fix the sound emission pipe directly on an exhaust pipe of the exhaust system in order to be able to introduce the sound waves generated by means of the actuator directly into the exhaust gas stream. Further, the actuator can be springily connected with a vehicle structure via its housing, such that the actuator can vibrate in relation to the vehicle structure together with the exhaust system. Because of confined installation situations, it is frequently not possible to fix the actuator directly to the exhaust system via the sound emission pipe. In these cases, it is basically possible to fix the actuator overall to the vehicle structure and to arrange the sound emission pipe detached in the surrounding area. As an alternative, it is also conceivable to connect the sound emission pipe with an exhaust pipe via a springy connection piece in order to be able to arrange the housing of the actuator at a different, more suitable site.
In the cases, in which the housing does not have a rigid or inflexible coupling with the exhaust pipe via the sound emission pipe, there is the risk that the housing is offset in vibrations during the operation of the actuator. In a rigid connection of the housing to the vehicle structure, the vehicle structure may consequently also be excited locally to vibrate, which may lead to an undesired development of noise in the vehicle. The vibration excitation of the housing can be attributed to the fact that the loudspeaker with its cage is ultimately supported on the housing. The cage stretches a diaphragm of the loudspeaker, on the one hand, and, on the other hand, carries an electromagnetic driver, which is drive-connected with the diaphragm. Each vibration introduced into the diaphragm by the driver acts as an “action,” whose “reaction” must be supported by the driver via the cage on the housing.